1. Field of the Invention
The present invention relates generally to an impeller, and more particularly to a centrifugal fan incorporating the impeller for dissipating heat generated by electronic components.
2. Description of Related Art
With the fast development of the electronics industry, electronic components such as CPUs (central processing units), or VGA (video graphics array) are being made with ever faster operating speeds. During operation of the electronic components, a large amount of heat is generated. Greater emphasis is now being laid on increasing the efficiency and effectiveness of heat dissipation devices so as to keep operational temperature of the electronic components within a suitable range.
Conventionally, a fan is used in combination with a heat dissipation device to produce an airflow in order to remove heat from the electronic components. Since most of electronic systems that contain electronic components therein such as a laptop computer, or a notebook computer do not have enough space therein, a centrifugal fan which requires only a small space for installation is generally used, wherein the centrifugal fan includes a housing, a hub and a plurality of blades extending radially from the hub. A first air inlet and a second air inlet are defined in central portions of top and bottom surfaces of the housing respectively, and an air outlet is defined in a side wall of the housing and is oriented perpendicularly to the air inlets. In use, the blades of the centrifugal fan rotate to engender the airflow towards the electronic component, thus cooling the electronic component continuously.
The diameters of the first and second air inlets are equal to each other and are both smaller than the diameter of the fan blades. For avoiding friction between the fan blades and the housing, a clearance must be defined between each of the top and bottom surfaces of the housing and the fan blades, which conflicts with the requirement for the fan blades to fully make use of the limited space in the electronic system in which the centrifugal fan is mounted. Additionally, for increasing the heat dissipation effectiveness of the centrifugal fan, a general way is either to increase a revolving speed of the fan blades or to change the shape of the fan blades in order to relatively increase the amount of the airflow. However, increasing the revolving speed may cause a noise of the fan to rise correspondingly, while changing the shape of the fan blades requires redesign of the fan blades and is difficult to achieve.
What is needed, therefore, is an impeller and a centrifugal fan with the impeller which can overcome the above-mentioned disadvantage.